Regarding a method for sharing information in a highly confidential conference or the like, various methods have been proposed.
An electronic conference system, for example, is proposed in which only a user or a terminal that has received authorization and registered in a server can access to a conference information server (for example, refer to Patent Document 1). Further a method for delivering documents to be used in an electronic conference is proposed, where the document to be used in the electronic conference can only be accessed from a terminal installed with a portable key device (for example, refer to Patent Document 2).
Further in an electronic conference system utilizing a wireless system, a method is proposed where only conference terminals received authentication keys transferred previously to the conference can attend the conference in order to prevent the connection from a terminal of other than permitted conference attendants (for example, refer to Patent Document 2). Further, for example, another method is proposed where conference documents can be read only in the conference room by utilizing a wireless LAN and limiting the access to the document only in specific space area (for example, refer to Patent Document 4).
Further, in pay-TV system which allows only contractants to view the contents, a method of specifying a time limit to be able to view the contents is proposed, where by broadcasting the contents in scramble and attaching data of viewable time limit to the scrambled information, reproduction or viewing the contents is made unable outside the viewable period (for example, refer to Patent Document 5).
In contrast, in a highly confidential conference, another method can be considered where documents are only displayed by a projector in a conference room, and the documents are not delivered to attendants.
Patent Document 1: Unexamined Japanese Patent Application Publication No. H08-256145;
Patent Document 2: Unexamined Japanese Patent Application Publication No. 2002-41461;
Patent Document 3: Unexamined Japanese Patent Application Publication No. 2004-96495;
Patent Document 4: Unexamined Japanese Patent Application Publication No. 2005-18487;
Patent Document 5: Unexamined Japanese Patent Application Publication No. 2000-196546.